Bias generating matrix



June 25, 1957 .1.A. RAJCHMAN Erm. 2,797,321

BIAS GENERATING MATRIXi original Filed nec. 1, 1949 :s sheds-sheet 1v(Vb: i A Y (yf, @w21 gw@ [gr/min ma INvEN'roRS eanA.

June 25, 1957 J. A. RAJCHMAN E TAL 2,797,321

BIAS GENERATING MATRIX Original Filed Dec. l. 1949 3 'Sheets-Sheet 2 i:inventors JMA. Ilma,

Jne 25, 1957 J. A. RAJCHMAN ETAL BIAS GENERATING MATRIX Original FiledDec. l, 1949 3 Sheets-Sheet 3 (lttorneg States BIAS GENERATLJG MATRlXJan A. Rachman and Max H. Mesner, Princeton, N. l., and MiltonRosenberg, Santa Monica, Calif., assignors to Radio Corporation ofAmerica, a corporation of Delaware 4 Claims. (Cl. 25d-27) This inventionrelates to vacuum tube matrices and more particularly to vacuum tubematrices for generating bias voltages.

This application is a division of application Serial No. 130,412, filedDecember 1, 1949, now Patent No. 2,666,161, for a Bias GeneratingMatrix.

In an application for an Electronic Discharge Device by J an A.Rajchman, tiled September 30, 1949, Serial No. 118,758, now Patent No.2,635,201, there is described and claimed a target area selection typeof tube. This is an improvement over the similar type of tube which isdescribed and claimed in a copending application for an ElectronicDischarge Device, Serial No. 665,031, tiled April 26, 1946, by Jan A.Rajchman, which is now Patent No. 2,494,670. The type of tube describedis a memory tube in which any discrete area of a storage target may beselected, as desired, for bombardment by electrons from the electronsource for the purpose ot either storing information in that area orreading the information stored therein.

One of the novel features of both of these types of tubes is theselecting grid structure which provides a facile means for selecting anydesired area `of the storage target for the purpose of being bombardedby electrons from the cathode. This grid structure essentially consistsof a first network of parallel, spaced, separately insulated conductorsand a second network of parallel, spaced, separately insulatedconductors. The conductors of the first network are angularly disposedwith reference to the conductors of the second network. Preferably, theangle made by the conduct-ors of the two networks is a right angle andthe conductors are accordingly known as horizontal selecting wires andVertical selecting wires. When viewed from the cathode looking towardthe target, these horizontal and vertical selecting wires deine aplurality of Windows through which electrons from the cathode pass onthe way to the storage target.

Whether or not electrons pass through any 'one window depends upon thebias existing on the four selecting bars defining that window. Adetailed explanation of the theory involved is found in the applicationfor an Electron Discharge Device, tiled April 26, 1946, by Jan A. Raich-Inan and bearing Serial No. 665,031, now Patent No. 2,494,670. In theapplication Serial No. 118,758, filed September 30, 1949, now Patent No.2,635,201, for an Electronic Discharge Device, it is shown and explainedthat, when the four selecting wires defining a window are at cathodepotential, electrons may pass through that Window, but, when any one ofthe four selecting wires is suiciently negative with reference to thecathode, then the window is closed to the passage of electrons. Thetarget is constructed with storage areas opposite these windows. Throughthe application of a proper bias to the selecting wires, one window maybe left open and all the others closed. It is thus possible to select asingle storage area for electron bombardment.

One system for applying a proper bias to the selecting latented .inne25, 1957 wires is to bring a lead from each one of the selecting wiresexternal to the tube envelope and to apply a proper bias to each ofthese leads so that either a desired window is left open and theremainder are closed, or all the windows are `open depending upon thecondition desired. It should be obvious that, with a tube having a largenumber of windows and therefore selecting wires, a cornplex andcumbersome arrangement is required-for applying a bias to these wires.However, systems have been developed for interconnecting the verticalselecting wires and the horizontal selecting wires in combinatorialcombinations inside the tube envelope so that, although the number ofleads required to be brought external to the tube is considerablyreduced, complete control in selecting a desired Window is provided.Systems for interconnecting the selecting wires in a combinatorialcombination are described and claimed in both the above notedapplication for an Electron Discharge Device and in an applicationSerial No. 694,041, filed August 30, 1946, by George W. Brown forControl of Electron Discharge Device of Area Selection Type, and nowPatent No. 2,519,172.

Although the number of leads, brought external to a tube for applying abias, is considerably reduced where the selecting wires are internallyconnected in a combinatorial combination, the problem of providing asystem which is simple to construct and operate and which permits theapplication of bias voltages selectively to these external leads isstill present. A number of systems, for applying bias to a selectinggrid for the purpose of opening a desired window, are described andclaimed in an application Serial No. 702,775 for Scanning Circuits forArea Selecting Tubes and the Like, by I an A. Rajchrnan, tiled October11, 1946, now Patent No. 2,558,460, issued June 26, 1951. These systems,however, are `desirable for scanning the target of an area selectingtube in a desired sequence and do not readily lend themselves to aselection of a desired window without going through a sequence. Thesesystems are also complex in operation and construction.

It is an object of the present invention to provide a bias voltagegenerating matrix which permits selective bias control.

It is a further object of the present invention to provide a biasvoltage generating matrix which is simple to construct and operate.

These and further obje-cts of our invention are achieved by providing abias generating tube for each biasing lead brought external to the tubefrom the combinatorial interconnection of the selecting wires in thetube. A plurality of first gate and second gate tubes are also providedwhich are equal in number to the number of bias generating tubes. Eachof the rst gate and second gate tubes have a common plate load to whichthe control grid of an associated bias generating tube is coupled. Therst gate tubes are normally conducting and thus the bias generatingtubes are normally cut olf and the bias lead coupled to its platereceives its most positive voltage. The second gate tubes are multi-gridtubes. Similar grids of groups of second gate-tubes are connected inparallel and then coupled to a plurality of multivibrators. In one ofthe groups of second gate tubes, each tube also shares a common cathodebias resistor with an associated single gate tube. The conductivecondition of these single gate tubes is determined by a multivibrator towhich the single gate tubes control grids are coupled.

The multivibrators used herein are of the two stable condition type. Bythe judicious application of a signal to each of the multivibrators,each multivibrator is placed in one of its two conditions of stabilitythus in turn applying signals to the associated second gate tubes tocause 'desired ones of the second gate tubes to be in a conductingcondition and the others of the second gate tubes to be in anon-conducting condition. A signal may then be applied to all the firstgate tubes to simultaneously render them non-conducting. In View of thecommon plate loads for the first gate and second gate tubes, when allthe first gate tubes are rendered non-conducting, a positive pulse isapp'lied to the control grids of all the bias generating tubes exceptthose associated with the second gate tubes which are selected to bemaintained in a conducting condition. The positive pulse applied to thebias generating tubes causes them to draw current and their anodesaccordingly go negative and bias the associated bias leads negative. Thebias generating tubes which are associated with the conducting secondgate tubes are unaffected and maintain a positive bias on the associatedbias leads. The bias leads which are maintained at the positive bias areconnected to the selected wires which define the window which is desiredto be kept open to the passage of electrons from the cathode to thetarget. The remaining windows are closed by virtue of the negative biasapplied to the remaining bias leads.

The novel features of the invention, both as to its organization andmethod of operation will best be understood from the followingdescription, when read in connection with the accompanying drawings, inwhich,

Figure 1 is a diametral section of an electronic discharge device, anunderstanding of which is necessary for an understanding of ourinvention,

Figure 2 is a schematic diagram of a system of interconnection of thevertical and horizontal selecting wires and their connection to theexternal bias leads, an understanding of which is necessary for anunderstanding of our invention,

Figure 3 is a circuit diagram of a selective bias generating matrixconstituting an embodiment of our invention, and

Figure 4 is a diagram showing all possible combinations of signalssupplied by multivibrators in the matrix and the leads which are biasedpositive as a result of each signal combination.

The diametral section of the target area selecting type of tube, shownin Figure 1, as well als the schematic diagram of a combinatorialinterconnection of its vertical and horizontal selecting wires are bothshown, described and claimed in the copending application of I an A.Rajchman, Serial No. 118,758, now Patent No. 2,635,201 filed September30, 1949. They are both reproduced and explained here to facilitate theexplanation of the selective bias generating matrix which constiutes anembodiment of our invention.

Considering Figure 1, it may be seen that the tube is in a glassenvelope and is constructed symmetrically about a plane formed by thecathodes 12. The catho'des 12 are preferably of a rectangular crosssection. The cathodes 12 are alternate with, between and parallel to aset of nine vertical selecting bars or wires 14 of square cross section.They are also substantially co-extensive with the vertical selectingwires 14. On either side of the plane made by the cathodes 12 and thevertical selecting bars 14 is a set of 18 parallel horizontal selectingbars 16 of square cross section. These two sets of horizontal selectingbars are parallel to, and sandwich the cathodes and vertical bars, as doall the subsequent electrodes of the tube.

It will be readily appreciated that, when viewed perpendicularly to theparallel planes formed by the vertical and horizontal selecting bars, agrid mesh is seen having square openings or windows in which thehorizontal sides are defined by two adjacent horizontal selecting barsand the vertical sides are defined by two adjacent vertical selectingbans. These windows are perpendicular to the path of the electrons fromthe electron source to the target and electrons -may pass through them.

Spaced on either outer side of the horizontal selecting Vbars 16, andparallel to the plane thereof, is positioned a plate.

first target assembly 24. This first target assembly consistis of acollector electrode 18, a storage target and a writing electrode 32. Thecollector electrode 18 is made of two fiat metal plates 20, 22perforated with round holes, the centers of which are aligned with thecenters of the windows formed by the vertical and horizontal selectingbars. The iirst plate 20, which is nearest the horizontal selectingbars, is known as the collector mask and has the lsmaller holes. Thesecond plate, or collector spacer 22, is in intimate contact with thecollector mask and has the larger holes.

On the outer side of each of the collector electrodes 18 is positionedthe storage target assembly. This consists of two perforated sheets 26,28 of an insulating materiail, such as mica, holding between them, bymeans of the perforations, metallic eyelets 30. Next cornes anothermetallic plate with aligned perforations which is known as the writingplate 32. The eyelets 30 are generally cylindrical and have shoulderoffset portions to be insulatingly retained thereby by the perforatedmica sheets. The perforations in the insulating sheets 26, 28 are sospaced as to position the eyelet openings opposite the center of therespective grid windows. An eyelet comprises a conical head, a centerhole, a collar and a tail. The writing plate 32 is separated from theeyelets 30 by the insulating material sheet 28 and serves as a commoncapacity plate for all the eyelets 30 with which it is associated. Thetwo collector plates 20, 22, the two insulating sheets 26, 28 supportingthe eyelets 30 and the writing plate 32 form a tight assembly which isriveted together at the upper and lower ends and in the center. 'Thistarget assembly 24 is more fully shown and described in Patent No.2,604,606, issued July 22, 1952, entitled Target for Storage Tubes, toIan A. Rajchman.

On the outer side of either target assembly 24 and spaced therefrom is asecond target assembly 25 consisting of a reading plate 34, which isanother metallic plate, having perforations substantially aligned withthe centers of the windows formed by the horizontal and verticalselecting bars.

Beyond each of the reading plates is a Faraday cage 36. This comprises arectangular metallic box in which two walls are parallel to the readingplate and have perforations aligned with the reading plate perforations,A glass plate 38 coated with a fluorescent and secondary electronemitting material 40, such as willemite, is placed against the outerperforated wall of the Faraday cage. In the central plate of the cagethere are nine reading wires 42' which are positioned so that they arebetween the perforations in the perforated walls and are thus shieldedfrom any electrons which may be coming directly from the target. Thereading wires are also substantially shielded from electrostatic fieldleakage from the reading These reading wires are connected together andthe corresponding lead to the stem of the tube is shielded. This secondtarget assembly 25 is also more fully shown and described in the aboveidentified Patent No. 2,604,606, entitled Target for Storage Tubes.

In Patent No. 2,494,670 for Electronic Discharge Devices, there has beenexplained at length the method by which the selection of an area of atarget is made by applying the proper bias to the selecting barsdefining the window which opposes the target area selected. Referenceshould be made thereto for detailed consideration of the subject.Briefly, however, it is explained therein that,

when all four selecting bars defining a window are at cathode potentialor higher, electrons can pass through that window. Should any one of theselecting bars defining the window be at a potential which issufficiently lower than cathode potential, then electrons do not passthrough that window but are deflected therefrom. This assumes that thereis a sufiicient accelerating potential exerted on the electrons toenable them to pass through the window when the defining selecting barsare at cathode potential. In order to secure the required acceleratingamasar potential in the area selecting type of tube described in theprevious above noted application, in one form, the selecting bars areall positively biased to permit the passage of electrons therethrough,and have their bias lowered to cathode potential or slightly negative toblock electron passage. In another form, positively biased, acceleratingelectrodes are interposed both between the horizontal and Verticalselecting bars and between the cathode and the selecting bars and theselecting bars are then either biased to cathode potential to permitpassage therethrough of electrons or are biased highly negative to blocksuch passage. The provision of a sufficient accelerating potential isthus provided either by the selecting bars themselves or theaccelerating electrodes.

In the tube described above, because of its structure, the collectorplate 18, which is positively biased, acts to provide the requiredaccelerating potential, In order to permit passage of electrons from thecathode' through a window, the selecting bars defining vthat window areleft at cathode potential. The biasing of any of the selecting barsdening a window suiciently negative with respect to the cathode preventsfurther passage of electrons through that window. Since the twopotential values applied to the selecting bars are either cathodepotential or a negative potential with respect to the cathode, it willbe appreciatexl that the power requirements for the selecting bars isminimal, since these bars never draw any current. Furthermore, thecathode potential is easily attained with accuracy in external circuits,while the negative voltage is not critical.

For biasing purposes, each of the vertical 14 and horizontal selectingbars 16 may be individually insulated and brought out through theenvelope of the tube and separately biased so that the window opposingthe desired target area is opened. Methods for effecting complete`control of the windows defined by the vertical and hon'- zontalselecting bars utilizing a number of external leads which is less thanthe number of horizontal `and vertical selecting bars have beendescribed and claimed in an application, Serial No. 702,775, filedOctober 11, 1946, by I an A, Rajchman, now Patent No. 2,558,460, and inthe application of George W. Brown, Serial No. 694,041, filed August 30,1946, now Patent No. 2,519,172 and -assigned to this assignee.

The principle of the combinatorial connections, by means of which thenumber of external leads can be greatly reduced, is the fact that, theelectron current through a gate, formed by two metal bars, can becontrolled by either bar. In the case of the window, any of the fourdefining bars can block the electron current. ln the present system the'stoppage of current is `actually `affected by suppressing almosttotally the emission from the particular area of the cathodecorresponding to a Window by biasing any one of the horizontal orVertical bars forming it. The small remaining part, perhaps l percent,is so badly deflected off the direction of the axis of the hole that itstrikes one face of the collector electrode 18 without reaching theeyelet 30.

Referring to Figure 2, wherein is shown a preferred system of connectionof the selecting bars, the nine vertical selecting bars 14 are connectedto six separate leads which are brought external to the tube. These'leads are in two groups and are designated as V1, V2, V3, V4 and V1 andV2. The thirty-six horizontal selecting bars are connected to twelveseparate leads which are brought external to the tube. These leads arealso in .two groups and are designated H1, H2, Hs, H4, and H1', Hz',H3', H4', H5', Hs', H7', and Hs. The nine vertical selecting bars '14are employed to operate as eight gates since there ,are only eightcombinations of V1, V2, V3, V4 and V1 and Vz, when any one of the Vs andany one of the Vs is taken (4X2). The 36 horizontal selecting bars areemployed to operate as 32 gates since there are only thirty-twocombinationsof H1, H2, H3, H4 and H1' through Ha', when one of the Hsand one of the Hs is taken (4X8). The excess number of bars are usedto-take care of the end elects. The eight vertical gates and 32horizontal gates separately control 256 windows. For operation of thetube as a two channel device leads H1 and H5', H2' and Hs', H3 and H7',and H4 and Hs' should be connected together.

Because of the positioning of the vertical selecting bars adjacent eachcathode and also the horizontal selecting bars adjacent the cathode, allthese bars being at cathode potential, and because of the positivecollector plate, with its holes in register with the windows formed bythe selecting bars, an almost perfect electron optical system is formed,Emission from the cathode is sharply focussed through the collectorhole. No current lgoes to the vertical and horizontal selecting barsbecause of this focussing and because they are at cathode potential.Furthermore, because of the sharp focussing action, Veryfew electronsstrike the collector plate but-most of them are directed throughthe'perforations and atthe storing eyelets 30.

In the quiescent state of the tube, the vertical and horizontalselecting bars are all at cathode potential and the collector plate 18is positively biased with reference thereto. The electrons emitted bythe cathodes will therefore be focussed into 256 beams by the combinedaction of the Vertical andhorizoutal selecting bars which form 256windows. These 256 beams are focussed through the center of thecollector holes and are directed at the heads of the eyelets 30.

The act of writing or reading requires the selection of one eyelet 30 ortarget element (two eyelets or target elements if the two halves ofthetubes are run in parallel). This selectionis obtained by applying anegative pulse to all the selecting leads except to the one in each ofthe four groups V, V, H and H which connect to the selecting barsdefining the window associated with the desired eyelet. These leads areleft at cathode potential.

For positive writing, a window to a desired eyelet is left open and theremaining windows are closed. A highly positive pulse is then applied tothe writing plate and is then allowed to slowly subside.

This pulse should have a sharp rise time, this rise time beingsufficiently short in order to overcome the locking electron current tothe eyelet. The amplitude of the pulse should be sufficient to drive theeyelet potential above the collector potential. In other words, thedisplacement current due to the capacity plate pulse should be greaterthan the locking electron current to the eyelet from the cathodes.During the plateau time or" the pulse the real current to the eyeletwill then charge the eyelet down to anode voltage. r)The writing platepulse then is permitted to decay slowly. The real current to the eyeletduring the decay period is now greater than the displacement current andthe eyelet as a result is locked at collector potential. The eyelet thenremains at a positive or approximately collector potential.

If it is desired to write negatively on an eyelet, the above outlinedprocedure is repeated except that before the pulse applied to thewriting plate is allowed to` decay, the window to the eyelet is closedby applying a negative pulse to one or more of the leads in the groupsV, V', H, H', which, during selection were left at cathode potential tokeep open the window associated with the selected eyelet. After the endof the writing pulse, all other pulses are ended and current isre-established to all the eyelets again.

The reading or interrogating of the tube is done one eyelet at a time(or two if the tube is used as a two channel device). First, a selectingpulse is applied to all leads to the selecting bars except the one ineach of the groups V, V', H and H' which is connected to the selectingbars defining the window associated with the eyelet desired to be read.Some arbitrary short safety period thereafter, a positive reading pulseis applied to the reading plate which was previously negatively biased.A pulse of electron current flows to the reading wires as a ,result Yofthis reading pulse if the selected eyelet isat ,collector potentialv butno electron current Viiows ifthe ing plate holes, through the Faradaycage 34 until they strike the uorescent screen 40. The area of thescreen defined by the holes in the Faraday cage 36 fluoresces andsecondary electrons are emitted and are attracted to the reading wires42. Thus a visual, as well as an electrical indication, is given as towhether an eyelet is at collector t or cathode potential. The readinghas no effect on the eyelet potential.

Figure 3 is a circuit diagram of the bias generating matrix by means ofwhich bias voltages for proper operation of the selecting grid aresecured. In the combinatorial connections shown in Figure 2 it may beseen that there are four groups of bias leads brought external to thetube. A first group has eight leads designated as H1', Hz',-H3', H4',Hs', H6', H7' and Hs', a second group has four leads designated as H1,H2, H3 and H4, a third group has four leads designated as V1, V2, Va,and V4, and a last group has two leads designated as V1 and V2'. Onelead in each of these four groups must be at the most positive potential(in this instancecathode potential) when the other leads are'at anegative potential in order that a single Vwindow be open. Y

A bias generating tube 50 is provided for each of the bias leads in thefour groups H', H, V, V. Each of the bias generating tubes 50 has itsindividual load resistor .52 connected to its anode 54. The leads areconnected to the anodes 54 of the bias generating tubes 50 and are shownas stub leads having the same designations as the leads in Figure 2. Itis to be understood that the leads of FigureV 2 and Figure 3, which aresimilarly designated, are connected together. A first gate tube 60 and asecond gate tube 70 are provided for each bias generating tube 50. Thefirst gate tubes 60 and the second gate tubes 70 each have a common loadresistor 62 connected to their anodes 64, 72. The cathode 56 of eachbias generating tube is connected to the B| supply for the first andsecond gate tubes. The control grid 58 of each of the bias generatingtubes is connected to the common anode connection of the first andsecond gate tubes to derive a control signal therefrom.

All the first gate tubes 60 are normally in a conducting condition. Thisresults in a more negative signal being applied to the control grids 58of the bias generating tubes 50. As a result, the bias generating tubesare nonconducting and the biasA applied to all the bias leads is themore positive one. Therefore, since all the selecting wires connected tothe bias leads are at their most positive condition, all the windowsformed by the selecting wires are open. All the cathodes 66 of all firstgate tubes 60 are connected to ground. The control grids 68 of the firstgate tubes associated with the first bias lead group H are all connectedto a first, two-position switch 61 which normally is in the positionwhere it is connected to a low impedance negative pulse source 69. Thecontrol grids 68 of the first gate tubes 60 associated with the secondbias lead group H, the third bias lead group V and the fourth bias leadgroup V are also respectively connected to second, third and fourthtwo-position switches 63, 65, 67 which are also normally connected tothe low impedance negative pulse source 69. The second position of allthe switches 61, 63, 65, 67 connects all the control grids to ground toisolate them from the effect of negative pulses from the source 69. Uponthe arrival of a negative pulse from the negative pulse source 69 allthe first gate tubes, in any. group whose switch Vis thrown to its firstposition are. rendered non-conducting.

All of the second gate tubes 70 are multi-grid tubes.

All their screen grids are connected together and to the B| sourcethrough a resistor 77. Considering first, the Veight second gate tubes70 associated with the first group of bias generating tubes andbiasleads, the suppressor grids 74of alternate second gate tubes 70 areconnected together. The two sets of four suppressor grids 74 connectedtogether are then respectively coupled to the two grids 92, 94 of afirst multivibrator 90. The control grids 76 of alternate second gatetubes are also connected together and the two sets of four control grids76 are respectively coupled to the two grids 102, 104 of a secondmultivibrator 100. The reason for connecting to the grids instead' ofthe anodes of the multivibrators is that the grids are at the proper D.C. level.

A single gate tube 80 is provided for each second gate tube 70 in thefirst group. Each of the second gate and associated single gate tubeshave their cathodes 78, 82 connected together and have a commoncathoderbias resistor 84. Therefore, in addition to the signals appliedto the suppressor 74 and control grids 76 of the second gate tubes 70,another signal is applied to the cathodes 78 by means of the single gatetubes 80,

In order for any second gate tube 70 in the first group H to be renderedconducting, a positive signal must be applied to its suppressor andcontrol grids 74, 76 and no positive signal should be applied to itscathode 70. A positive cathode signal is applied when the single gatetube is conducting. If a single gate tube is non-conducting, then theconductivity of the second gate tube is determined by the signals on itsgrids. The control grids 86 of the rst, last and middle two of thesingle gate tubes 80 are connected together. The control grids of theremaining single gate tubes 80 `are also connected together. These twosets of interconnected control grids are then coupled to the two grids108, `of a third multivibrator 106 through a pair of D.C. coupled butteramplifiers 96, 98. The anodes 80 of the single gate tubes 80 `areconnected to the same B-fsource as are the first and second gate tubes.The D.C. coupled buffer amplifiers 96, 98 are required to raise the D.C.level of the signal applied to the single gate tubes in order that thepositive signal, which is applied to their grids, have sufficientamplitude to maintain the single gate tubes conducting and thus bias offthe second gate tubes 70 regardless of any other signals which may beapplied to the second gate tubes control grids.

For the second bias lead group H only four bias gen,- erating tubes 50and associated four first gate 60 and four second gate tubes 70 arerequired. The connections between these tubes are the same as theconnections in the first group H. It will be noted, however, that nosingle gate tubes are provided for the second gate tubes. Instead thecathodes 78 of the second gate tubes are returned to ground. The controlgrids 76 of alternate second gate tubes are connected together and thenconnected to the grids 114, 116 of a fourth multivibrator 112. Thesuppressor grids 74 in the alternate second gate tubes 70 of the secondgroup H are likewise connected together and coupled to the grids 120,122 of a fifth multivibrator 118.

The third bias lead group V also contains four bias generating tubes 50,four first gate 60 and four second gate tubes 70 which areinterconnected in a fashion similar to the interconnections of thesecond bias lead group H. A sixth 124 and seventh multivibrator 130 areprovided which are coupled to the suppressor and control grids. However,the control grids 76 are coupled to the sixth multivibrator 124 throughbuffer amplifiers 142 paralleled by triodes 146 for `reasons which aresubsequently explained herein.

The fourth bias lead group V' requires only two bias generating tubes 50with two associated first 60 and second gate tubes 7 0. The suppressorgrids 74 of the second gate tubes 70 are connected to ground through aresistor 71 and also to a negative pulse source 73 for reasons whichwill be subsequently explained herein. Each con- 9 trol grid 76 iscoupled to oneof the grids 138, 140 of an eighth multivibrator 136. i

Each one of the eight multivibrators are of the type, well known to theart, having two tubes `including cross connected grids and Yanodes, twoconditions of stability, and are capable of being triggered from onecondition oi stability to the iother condition of stability by pulses ofthe proper polarity applied to the control grids. The theory ofoperation of the multivibrator is well known and may be found explainedin a book, Theory and Applications of Electron Tubes by H. J. Reich,published by McGraw-HillV Book Company, pages '362-365. A typicalmultivibrator circuit is shown for the lirst multivibrator; theremaining seven multivibrators are represented vestigially in dottedline boxes.

From'the foregoing explanation it will be appreciated that, when all theVfirst gate tubes 60 are conducting, current is drawn through all theircommon load resistors 62 'thus causing the bias generating tubes S0 toapply a more positive bias to the bias leads. When the 'rst gate tubes60 are rendered non-conducting by throwing the fourswitohes 61, 63, 65,67 to the second position, the bias voltages applied to the leads by thevarious bias generating tubes 50 are determined by the conducting ornon-conducting condition of the second gate tubes 70. If a second gatetube is in a conducting condition, current is still dnawn through thecommon load resistor 62 when the associated rst gate tube is renderednon-conducting and the associated bias generating tube will still applya more positive voltage to its bias lead. However, should a second gatetube 70 be in a non-conducting condition, when a first gate tube 60 isrendered non-conducting, the anodes of both of these tubes rise up tothe value of their B+ supply. Therefore, la positive pulse is applied tothe bias generating tube grid 68 causing the tube to draw current andthus apply a negative pulse to the associated bias lead and theselecting bars connected thereto. This lin turn closes the windowscontrolled by these selecting bars to the passage of electrons.

The condition `of conduction of each of the second gate tubes isdetermined by the signals impressed on these tubes by the eightmul-tivibnators. In an actual electronic computing machine, the settingof these eight multivibrators is determined by a coded set of voltages,which is obtained from the coded input circuit S of the computer and isimpressed upon the grids of the multivibrators. The signal from thecoding circuit is a short sharp pulse whose duration is just long enoughto trip the multivibrator and not alt'ect the signal on themultivibrator grid from the anode to which the grid is cross connected.

Referring to Figure 4, there is illustrated the selection effect of thesignals derived from the grids of the eight multivibrators. Fourrectangles are shown, one for each group H', H, V, V. ln each `rectangleare two vertical columns representing the grid signals supplied by eachmultivibrator in the group. The numeral at the heading of each verticalcolumn corresponds to the identifying numeral of the multivibrator grid,the signal being impressed on the associated second gate tube by themultivibrator grid is shown thereunder. At the right side oi thehorizontal column is shown, for the signal combination shown, the biaslead i-n each group which has a positive bias applied to it. All otherleads of the group have a negative bias applied. All possiblecombinations of signals applied by the multivibrators to the selectingbars are shown. By applying the proper coded signals, a single bias leadin each gro-up is selected to be maintained positive and all othersnegative. Accordingly, a single selected window, detined by the positive(cathode potential) selecting bars attached to these bias leads, is opento the passage of electrons while the remaining windows are closed.

For writing negatively on any target storage eyelet of the tube, it waspreviously explained that only a single window opposite the selectedeyelet is kept open, a positive pulse is applied to the writing plateand before this pulse can decay, the window is quickly closed to theflow of current. Some time after the positive -pulse has decayed, allwindowsare again opened. Several methods for closing the window areavailable and some of these are shown in Figure 3. One method is tocouple a source, which provides a negative or cutoff pulse whenrequired, to the suppressor grids of any group of second gate tubes.This is shown for the fourth group in Figure 3. The negative pulsek fromthe source '73 causes any connected conducting second gate tube 70 to becut off. The resulting negative bias voltage generated by the associatedbias generating tube is applied to one of the selecting wires which isalso one of the wires defining an open Window. The window is thereforeclosed.

Other apparatus, by means of which an open window may be closed, isshown in Figure 3 as serving to couple the control grids of the thirdgroup of second gate tubes to the sixth multivibrator 124. Thisapparatus consists of a pair of D.C. coupled ampliiiers 142, each havingan associated triode tube 146 whose anode 14S and cathode 150 Varecoupled to the associated D.C. amplilier anode 152 and cathode 154. Thegrids 156 of the triode tubes 146 are connected together and through anYisolating resistor to a negative bias source so Athat they are normallynot conducting. One of the D.C. coupled ampliers 142 is conducting andthe other is not conducting depending on the signal applied from themultivibrator grids. A positive pulse is applied from a positive pulsesource at the proper time to the grids of the triode tubes. This causesthem to conduct and draw current through the load resistors common toboth triodes and D.C. ampliers. The voltage drop, caused thereby at theanode of the D.C. amplifier, causes a negative pulse to be applied tothe control grid of Whichever second gate tube has been conductingcausing it to cease conducting. The end result is that the associatedbias generating tube applies a negative bias to one of the selectingwires deining an open window, thus closing the Window.

The B+ supply for the bias generating tubes may have its positive sideconnected to the cathode of the area selecting tube and its negativeside below cathode potential so that the more positive bias applied tothe leads when the bias generating tubes are not conducting is atcathode potential and the less positive bias applied when the biasgenerating tubes are conducting, is well below cathode potential.

There has been shown and described herein a bias generating matrixwherein the response of the bias generating tubes to the change in theconductive condition of rst gate tubes is determined by the conductivecondition of second gate tubes which in turn is determined by a codedsignal input.

From the foregoing description it will be readily apparent that aselective bias generating matrix has been described which readilypermits facile application of bias to a selecting type of grid to permitthe opening and closing of a desired window, defined by any four of theselecting wires, to the passage of electrons. Although a singleembodiment of the bias generating matrix has been herein shown anddescribed in connection with one type of selecting grid having fourgroups of interconnecting bias leads, it should be apparent that thebias generating matrix may be altered to accommodate other selectinggrid combinatorial interconnections or serve as an apparatus forproviding signals in response to coded input signals. It shouldtherefore be apparent that many changes may be made in the particularembodiment herein disclosed and that many other embodiments arepossible, all within the spirit and scope of the invention. Therefore,it is desired that the foregoing description shall be taken asillustrative and not as limiting.

What is claimed is: Y v

1. A matrix for the selectiveV generation ofrbias, voltages comprising aplurality of rst gate' tubes, Aa plurality of second gate tubes, each ofsaid rst gate tubes together with separate ones of said second gatetubes having a common load impedance, and a plurality of bias generatingvacuum tubes having at least a cathode,'an anode and a control grid, thecontrol grid of each of said bias generating tubes being coupled to aseparate one of said load impedances to derive therefrom a bias voltagecontrol signal, and means to control said second gate tubes to causeselected ones of said second gate tubes to assume one condition ofconductivity and simultaneously to cause the remainder of said secondgate tubes Vto assume a second condition of conductivity, therebyselectively to determine the bias voltage generated by each of said biasgenerating tubes.

2. A matrix for the selective generation of bias voltages comprising aplurality of normally conducting rst gate tubes, a plurality of secondgate tubes, each of said first gate tubes together with separate ones ofsaid second gate tubes having a common load impedance, a plurality ofbias generating tubes, each of said bias generating tubes having atleast a cathode, a control grid and an anode, the control grid of eachof said bias generating tubes being coupled to a separate one of saidload impedances to derive a bias control signal therefrom, means torender simultaneously non-conducting said plurality of normallyconducting first gate tubes, and means to render desired ones of saidsecond gate tubes conducting and the remaining ones of said second gatetubes nonand said generated bias voltages to diter accordingly.

j 3. A matrix for the selective generation of bias voltages as recitedin claim 2 wherein each of said second gate tubes has a cathode, ananode and a plurality of control grids and said means to render desiredones of said second gate tubes conducting and the remaining ones of saidsecond gate tubes non-conducting includes a plurality of multivibrators,each of the control grids in each one of said second gate tubes beingcoupled to a separate multivibrator.

4. A matrix as recited in claim 2 wherein said means to render desiredones of said second gate tubes conducting and the remaining onesnon-conducting includes in addition several vacuum tubes each having atleast cathode, control grid and anode electrodes, each also having acommon cathode bias resistor with a corresponding one of said secondgate tubes, the control grids of one half of said several vacuum tubesbeing connected in parallel and t0 one output from one of said pluralityof multivibrators, the remaining half of said several vacnum tubes beingconnected in parallel and to the other output of said one of saidmultivibrators.

References Cited in the tile of this patent UNITED STATES PATENTS2,541,932 Melhose Feb. 13, 1951 2,559,499 Gillette et al. July 3, 19512,611,813 Sharpless et al. Sept. 23, 1952 2,615,127 Edwards Oct. 2l,1952 2,666,848 Goodwin Ian. 19, 1954

